Application Of Anti-Progressive Collapse Analysis In Structural Engineering Design

For the buildings where people live and work, the structural safety is the mostimportant issue. Since1968, some serious progressive collapses occurred in both Chinaand foreign countries, which caused severe loss. The mechanism of progressivecollapse became research hot field. The progressive collapse initiates from the localdamage due to large or small accident loads, then the damage spreads outward andcauses chain reaction, finally, the large scale collapse happens. The final damage is notproportional to the initial damage completely. The following aspects in the progressivecollapse are mainly discussed:(1) Based on relationships of concrete and steel, the plane assumption, thestrength of concrete and steel bar, the area and position of steel bar, the size of section,and the relationship ofN Min ultimate state, the criterion of plastic hingecalculation is establish for rectangular reinforced concrete, circular reinforced concrete,concrete-filled steel tube and steel reinforced concrete. The coupling between bendingmoment and axial force in plastic hinge is also considered.(2) I participated the writing of the nonlinear frame analysis program. The verticalload, seismic load and wind load are considered. The increment method in nonlinearanalysis is adopted. The seismic load is found by the seismic response spectrum, anddistributed by reverse triangular. The load-horizontal displacement curve isautomatically given, and the sequence of plastic hinges forming is signed automaticallyalso.(3) When the structure becomes the movable mechanism, the structure can beregarded as collapse. But we do not take this criterion to judge the collapse of thestructure due to the calculation difficulty caused by the zero stiffness of the movablemechanism. A new criterion is put forward to determine the collapse: the stiffness ofthe given direction decreases to a low value, the structure is regarded as collapse, thecalculation is stopped. The definition of collapse is: the ratio of the stiffness of structureunder some grade load to the initial elastic stiffness is less than a low value inputartificially, the structure collapses. The primitive criterion of collapse is presented.(4) Based on the MATLAB graphic program, the calculation results are visualized,which demonstrate the response of the structure under various loads. (5)According to the SAFPH finite element program written by ourselves, two kindsof collapses are investigated, such as the collapse caused by horizontal seismic andwind loads; the collapse caused by occasional vertical load in accident.